Mercury lamp voltage control



April 19, 1960 R. F. WALSH ETAL 2,933,362

MERCURY LAMP VOLTAGE CONTROL 2 Sheets-Sheet 1 Filed Oct. 6, 1954 INVENTORS RICHARD E WALSH JOSEPH ROLAND MORIN FIG. 2

April 19, 1960 R. F. WALSH ETAL 2,933,352 I MERCURY LAMP VOLTAGE CONTROL Filed 001.. 6, 1954 2 Sheets-Sheet 2 RICHARD F WXFSH JOSEPH R LAND MORIN BY FIG. 6 M W 2,933,362 MERCURY LAMP VOLTAGE CONTROL Richard F. Walsh, Lynn, and Joseph Roland Morin, Ipswich, Mass., assignors, by mesne assignments, to Sylvania Electric Products Inc., Wilmington, Del., a corporation of Delaware Application October 6, 1954, Serial No..460,546 I 3 Claims. (Cl. 316-26) give a vapor densitycorresponding to a predetermined "voltage, the voltage will vary widely with changesin the operating temperature of the lamp, and hencewiththe ambient temperature of the atmosphere around the lamp. It is-accordingly customary to put into the lamp a quantity of mercury which when completely vaporized will give the desired voltage, and then to operate the lamp at currents giving a lamp temperature above the temperature at which all the mercury is vaporized. Variations in the lamp temperature will then not vary the lamp voltage unless the variation is so great as to reduce the temperature to a value such that some of the mercury begins to condense out on the tube wall.

The amount of mercury required for the usual voltages is so small, however, that itis ditficult to fix it with precision in a lamp and the amount" required fromlamp to lamp will in any event vary with slight changes the lam-p dimensions.

We have found, however, that'the amount can-be precisely fixed by operating the lamp with more mercury therein than necessary for the desired voltage, condensing the excess in a portion of an elongated exhaust tube, cooling the lamp and exhaust tube after the lamp voltage has attained a maximum and dropped to the desired value, and then scaling 015 the exhaust tube between the main lamp envelope and the portion of the exhaust tube in which the mercury has'condensed. This also improves lamp performance by the difiusion of residual contaminants into the portion of the exhaust tube which is sealed ofi.

Other objects, advantages and features of'the invention will be apparent from the following specification, taken in conjunction with the appended drawings in which: 1

Figure 1 is a perspective view of one embodiment of the invention; 7 I

Figure 2 is a perspective view of a modified embodiment;

Figure 3 is a view of several of the devices of Figure 2 arranged on a bench;

Figure 4 is a schematic circuit diagram of the lamp circuit;

Figure 5 is a schematic circuit diagram of the exhaust tube heater circuit; and

Figure 6 is a view of the sealing-01f of the exhaust tube.

In Figure 1, the lamp envelope 1 which can be of quartz, hard glass, or similar material, is supported by the metal clamps 2, 3 which are attached to its main lead-in wires 4, 5. A third lead-in wire 6, to an auxiliary electrode for starting the lamp, can be left unconnected as shown, it sufiicient voltage is available to start 2,933,362 Patented Apr. 19,

ice

the lamp without the use of that electrode. The clamps 2, 3 are attached, respectively, to their supporting metal rods 7, 8 which project from the plug 9, which may be of asbestos or other heat-resistant material.

The other two metal conducting rods 10, 11 are connected to the resistance wire 12 in heater 13 which fits over the elongated exhaust tube 14 but is short enough to allow the outer end of the exhaust tube 15 to project therefrom. The heater 13 can comprise a heater wire 12 and an enclosing tube of ceramic or other heat resistant material, the tube having a central cylindrical opening through which exhaust tube 14 can pass.

The plug 9 is supported from the heat-resistant plate 16, which also supports the magnet 17 above the lamp envelope 1. The magnet has a coil 18 from which leads 19 and 20 extend to and through the plate 16. A bracket 21 -is held to plate 16 and plate 22 by screws 23, and the magnet 17 is attached to the end of plate 22 by'the screws 24 through the laminated iron core 25 in coil 18.

The metal manifold 26 leads to the air outlets 27, 28 through pipe 29 and valve 66.

The glass outer envelope 30 extends around the inner envelope 1' and-fits over the plug 9, to reduce convection losses and to allow the lamp to heat quickly.

In Figure 2, the lamp envelope 1 is supported on heat resistant metal brackets 31, 32 which also serve as connections to lead-in wires 4 and 5. The heat-resistant box 34 surrounds the unit, with the cover 35 on hinges 36, and having the snapholder to hold it to box 34 when the cover is closed over said box. Openings 37, 38 are left in the bottom of the box for the cooling air. Heater 39 keeps exhaust tubing hot as in Figure 1.

Figure 3 shows several units of the type of Figure 1 set into compartments formed by the backplates 16 and partitions 40 between the units. Metal supports 41 extend upward from the floor (not shown), and the plates 16 are attached to them. They also carry a metal rod 42 which extends in front of the partitions and carries a cloth curtain 43 held thereto by wire loops 44, so that the curtain can be pushed aside while the lamp envelopes 1 are set in place in the partitions, and then pulled back into place to shield the light of the lamps from the observers eyes.

A metal cross-piece 45 supports a panel 46 carrying a voltmeter 47 for each lamp, and the toggle-switches 48, 49 for turning on the lamps and heaters 13, respectively. Another metal cross-piece 50 supports a shelf 51 on which the inductance coils 52 are mounted to serve as ballasts.

A variable reactor 53, controlled by knob 54, allows the across the lamp and an ammeter 62 in series with the lamp, as shown.

In Figure 5, the circuit to the heater coil 13 is shown, the heater being supplied from the variable auto-transformer 63 through ammeter 64. A voltmeter 65 is across the heater coil 13.

In addition to the features appearing in the drawings, the sealed lamp envelope 1, has the usual electrodes on the internal ends of the lead-in wires 4, 5, and has a filling of argon at about 8 mm. pressure and of mercury, the amount of mercury present being somewhat greater than that necessary to give the desired voltage when completely vaporized.

In operation, the lead-in wires 4, 5 of the sealed lamp envelope 1 are secured in the clamps 2, 3, and the heater 13 is placed around exhaust tube 15, the sealed-01f end oi the latter extending out of the heater. The open end of outer glass envelope 30 is pushed over plug 9 which holds it in place, and voltage is applied to the lamp circuitof Figure 4 and the heater circuit of Figure5. The magnet has been previously set in position to hold the are flame horizontal in the envelope 1, to prevent the flame from touching and cracking said envelope. 7

As the mercury is vaporized in envelope 1 by the heat of; the discharge, the voltage across electrodes 4, will rise and reach a maximum. All the mercury inenvelope 1, will then have been evaporated, except for whatever amount may be condensed out in the sealed-off end of exhaust tube 15. The heater 13 is adjusted to keep the mercury from condensing out of envelope 1 too quickly.

If the rate of condensation is too great, the lamp voltage will not reach a maximum during the process, and it will then be uncertainwhether or not all the mercury in the lamp envelope '1 has been vaporized. If the lamp voltage reaches a maximum and then drops to the desired value as mercury condenses out, the operator can then be sure that all the mercury inthe lamp envelope 1- is vaporized; At the starter the heating, all the mercury shouldbe in the lamp envelope 1, or at any rate the envelope should contain an excess of mercury over that necessary to give the desired lamp voltage, not including any ,mercury that may be then in the exhaust tube 14.

After reaching a maximum, the voltage will then begin to drop off and when it reaches the desired value for the lamp, the power to the electrodes 4, 5 and to the heater .13 is disconnected, The outer envelope 30 is then ;re- ;rnoved, and heater 13 is removed from the exhaust tube.

The device is then allowed to cool to room temperature. The cooling can be done more quickly if valve 66-is now. opened, allowing air to issue from nozzles 26 to be directed onto the lamp. The air-cooling step just described can be omitted if desired, and the lamp allowed to cool in the ambient-atmosphere.

A, The exhaust tube 14 is then sealed off by flames 67 from burner 68 at apoint nearer the main portion ofthe lamp envelope 1 as shown in Figure 6. The excess ;me rcury 69 will he removed with the excess portion 70 of the exhaust tube 14, as in Figure 6, and the amount of mercury remaining in the lamp will be the amount (giving the desired voltage. The same procedure can be used with the enclosing box of Figure 2, the lamp electrodes 4, 5 being secured to the metal supports 31, 32.

In one example of the invention, the lamp envelope 1 was about 7 inches long and 1% inch in diameter, the lead-in wires being .030 inch in diameter and about 1 inch out of the envelope '1. The exhaust tube 14 extended 3 inches out of the lamp at the start of the method and was sealed'ofi about 7 inch from the envelope 1 after the excess mercury had condensed in it.

The internal electrodes were of the usual oxide coated tungsten wire types customary in mercury lamps. A voltage of 220 volts was applied across the lamp for starting, and the series impedance, including the inductance 58 and magnet coil 17, was sufficient to pass a current of 6 amperes when the arc voltage was volts and the voltage applied to the circuit was 200 volts.

What we claim is: 1

1. The method of manufacturing a high. pressure mercury lamp to have a predetermined operating voltage, said lamp having an envelop e,electrodes therein, a quantity of mercury therein and an elongated exhaust tube extendingtherefrom, said method comprising: passing a current between said electrodes to heat said lamp and to vaporize the mercury therein, the passage of said current beingcontinueduntil the voltage rises to a maximumand then begins to fall; heating the exhaust tube only in the region nearestto said lamp in order to insure that the lamp voltage r'is'e's'to a maximum before it begins to fall, and allowing the ,remainder'of the exhaust tube to remain cool; discontinuing the passage of current when the voltage falls to the desired value; allowing the lamp andexhaust tube to cool; then sealing oflthe exhaust tube at a point such-that the mercury condensed in .the

exhaustrtube is sealed outof thelamp. I

2. The method of manufacturing a high pressure mereurylamp to haveapredetermined operating voltage,

said} lamp having an envelope, electrodes therein, a quanti-ty-ofimercury therein and anelongated exhaust tube extending therefrom, said-method comprising: placin'gsaid lamp with its longitudinal axis horizontal; passing a current between; the electrodes to heat said lamp and to vaporize the mercury therein, thepassage of said current being continued until the voltage'rises toa maximum and then begins to fall; heating the exhaust tube only in the region nearest to said lamp in order to insure that the lamp voltage rises to a maximum before it begins to fall, andallowing the remainder of the exhaust tube to remain cool; discontinuing the passage of current when the volt age falls to the desired value; allowing the lamp and exhaust tube to cool; then scaling 011 the exhaust tube meant; Cited in the file or this patent UNITED STATESPATENTS 2,208,115 Bonney et a1. July 16, 1940 2,374,304 Owings Apr. 24, 1945 2,401,734- Janes a June 11, 1946 2,456,396 Frohock, Dec. 14, 1948 2,730,424 Kenty et al. Jan. 10, 1956 2,755,159 Bernier etal July 17, 1956 Veith Oct. 8, 1957 

